To safely control the 110-VAC heating element through a remote DC switch, use a DC-AC solid-state relay. It's what I used when I added a 110-volt heating element to my Suburban water heater: https://www.roadtreklife.net/2016/03/120-volt-electric-conv...
Nice simple solution. I did same thing about a year ago, mine is electronically controlled and fully automatic, the system only activates when hot water reaches a certain set temperature. When you turn the water heater off, the system remains active ...
Look at Speed-Rail, different fittings and mounts (wall. floor) are available. You can also get painted Speed-Rail tubing for more finished look. You can replace the fitting set screws with thumb screw or lock pin for easy removal. That is what I us...
No doubt directional antenna will have better range than Omni antenna but you have to repoint and retune the antenna every time you connect to a different AP. I have Omni antenna on my Roadtrek running on 12 volts DC. Setup is more involved, but once...